The part of the heat pump that sits outside is roughly 1m x 1m x 2m (or to help you visualise - the size of a moped). It needs a space of around a meter in front and to each side to breathe.
Inside you need space for a hot water tank - 2m x 1m x 1m (the size of a modern fridge freezer), on the ground or first floor of your home (the closer to the heat pump the better).
The cylinder can also be installed in a garage, outdoors in a purpose-built store, or in the loft, but this may decrease efficiency (it takes more energy to heat the water when the cylinder is exposed to the cold).
Find out if a heat pump is the right fit for your home when you get an instant quote.